Recently virtio-9p support was added to bhyve.

On the host side it looks this way:

  bhyve .... -s 25:0,virtio-9p,sharename=/path/to/shared/dir

It could also have ",ro" suffix to make share read-only.

In the Linux guest, this share is mounted with:

  mount -t 9p sharename /mnt/sharename

In the guest user will see the same permissions and ownership
information for this directory as on the host. No uid/gid remapping is
supported, so those could resolve to wrong user or group names.

The same applies to the other side: chowning/chmodding in the guest will
set specified ownership and permissions on the host.

In libvirt domain XML it's modeled using the 'filesystem' element:

  <filesystem type='mount'>
    <source dir='/path/to/shared/dir'/>
    <target dir='sharename'/>
  </filesystem>

Optional 'readonly' sub-element enables read-only mode.

Signed-off-by: Roman Bogorodskiy <bogorodskiy@gmail.com>